DOVER — Jurors were given 75 minutes of instructions Thursday before being sent to decide whether Seth Mazzaglia is guilty of five charges, including murder.

Prosecutors say Mazzaglia strangled University of New Hampshire student Elizabeth “Lizzi” Marriott to death on Oct. 9, 2012, while in a rage fueled by her refusal to engage in a sexual threesome with him and his girlfriend, Kathryn “Kat” McDonough. Defense attorney Joachim Barth argues that Marriott was smothered to death during a consensual sexual threesome, during which McDonough sat on Marriott's face for 10 to 15 minutes.

Judge Steven Houran selected 12 jurors and four alternates and told them it's “up to you to decide what the facts are in this case,” based on law and without prejudice. He told them they cannot consider as evidence Mazzaglia's arrest or the allegations, that their decision should not include consideration of possible punishment, and that his right not to testify carries no weight. They were instructed to determine guilt beyond a reasonable doubt and told that lawyers' statements are not evidence,

Houran told the jury they should consider views they had of alleged crime scenes, sworn witness testimony and exhibits. Direct evidence, he explained, is direct proof of fact. Circumstantial evidence, the judge advised, “is indirect evidence.” As an example, the judge said if they see snow on the ground it's direct evidence that it's snowing. If they go to bed and don't see snow on the ground, but wake up to a snow-covered ground, it's indirect evidence that it snowed.

“If there's a conflict of testimony from witnesses, you must decide which witness to believe,” the judge said. “You the jury must decide which witness to believe. If you believe part of a witness' testimony was false, you can dismiss other parts of their testimony.”

Houran also explained that McDonough's immunity, given in exchange for a light sentence and her testimony, means she could not refuse to testify and that nothing she said at trial could be used against her, unless she lied.

“An immunized witness is subject to perjury if they gave false testimony,” he said.

“If there is any reasonable doubt,” the judge advised, “then you must find him not guilty.”

The judge explained five charges against Mazzaglia as follows:

* First degree murder: That Mazzaglia purposely caused the death of Marriott by strangling her. Houran said the charge alleges Mazzaglia wanted or intended to cause her death.

* A second, alternate charge of first degree murder: That before, during, or after a felonious sexual assault of Marriott, Mazzaglia committed the crime of first degree murder by strangling her. The judge said jurors must find that Mazzaglia caused Marriott's death, that he did so before, after, or while raping her, and that he acted knowingly. They must also determine that Marriott did not consent to sex, the judge instructed.

* A third, alternate charge of reckless second-degree murder: That Mazzaglia caused Marriott's death with extreme indifference to the value of human life by strangling her. Houran told the jury they can not find Mazzaglia guilty of first and second-degree murder, that it must be one or the other.

* Conspiracy to commit witness tampering: That Mazzaglia is guilty of one of the following allegations; He agreed with McDonough about how to cover up Marriott's murder, they concocted a false alibi, they gave Chester police false alibis about their whereabouts and lack of interaction with Marriott on the night of her death, they gave false alibis to state police, they schemed to say Marriott died during consensual sex, they planned to marry to avoid her giving testimony, they conspired to give Mazzaglia's defense team a false story, that Mazzaglia sent letters to McDonough with a “concocted story” about Marriott dying during consensual sex and was murdered by witness Paul Hickok, that Mazzaglia mailed McDonough a concocted story for her to memorize and destroy “for future tellings,” that Mazzaglia instructed McDonough to commit a false story to memory, that Mazzaglia sent letters with plots to kill witnesses, that he sent letters to McDonough suggesting she commit suicide and telling her how, that he wrote letters to her with plans to flee the country and alter their names and identities, and/or that Mazzaglia recruited an inmate to deliver letters with escape plans.

The judge told jurors they must find that Mazzaglia alone, or with McDonough, committed at least one of the above acts to find guilt.

* Conspiracy to commit falsifying physical evidence: That Mazzaglia committed one of the following; Agreed with McDonough to send a text message to Marriott's phone — after she died — to create a false impression, that he and McDonough deleted text messages from their phones about Marriott's visit to their apartment, that they concealed Marriott's dead body in a suitcase and tarp and removed it from their apartment, that they gathered Marriott's clothing, belongings and rope and removed it from their apartment, that they used Marriott's car to transport her body to Peirce Island, that they dumped Marriott's dead body into the Piscataqua River, that they broke Marriott's cell phone and GPS device and disposed of them, that they drove Marriott's car to the UNH campus and parked it there, and that they dumped evidence in Dumpsters.

The jury was excused for the day just before 4 p.m. and will reconvene Friday morning.